In the exploration of oil, gas and geothermal energy, drilling operations are used to create boreholes, or wells, in the earth. The wells must be lined with casing to support the rough drilled sides of the well and to prevent them from caving in. Casing also protects subterranean water reservoirs from pollution from the drilling fluids, and from the oil and gas being produced. The casing program for a well requires casing operations to occur periodically throughout the drilling process. They start with a conductor pipe, followed by surface casing, intermediate casing, and ending with string of production casing which takes place during well completion.
Conventional casing is manufactured in lengths called sections or joints that are about 40 feet long. The sections of casing are screwed together to form casing “strings.” Each end of a section of casing has male threads. A female threaded coupling is used to join the two male threaded sections together. Effort and equipment are expended to protect the threads of each casing section so that they may be securely connected to an adjacent casing section. Thread protectors are employed for this purpose.
Casing is run into the well from the drilling floor. Casing hangers are used to support the weight of the casing string at the top of the well. Centralizers are located on the casing to keep it centralized in the well.
Casing can be run into the well one section at a time, or in doubles or “stands” that are two sections of casing connected together in advance of running the casing in. Running stands is more time efficient as it eliminates the need to stop and connect 50% of the threaded connections. To run stands of casing, it is necessary to build them in advance, and to store them to be ready for use. Casing stands are conventionally stored vertically on the drill floor. Their upper ends are supported in the fingerboard of a mast-side racking module.
Thread protectors are used to protect the threads of casing sections. Handling individual thread protectors when running the casing string into the well takes time, as does managing the numerous thread protectors as they are removed. The need to run casing strings into the well faster creates additional problems as their positioning and alignment are primarily manual. There remains a need to control positioning of the lower end of casing stands in a manner that is accurate and protective of the casing threads.